Transcript Chapter 21 Section 2 Powerpoint

Cycles of Matter
Chapter 21- Section 2
Essential Questions
• What process causes water from the
surface of the ocean to enter the
atmosphere as water vapor?
• What role do producers play in the
carbon and oxygen cycles?
• Where do some nitrogen-fixing bacteria
live?
The Water Cycle
• Water is essential for life. To ensure a steady
supply, Earth’s water must be recycled.
• The water cycle is the continuous process by
which water moves from Earth’s surface to the
atmosphere and back.
• The processes of evaporation, condensation,
and precipitation make up the water cycle.
Evaporation
• The process by which molecules of liquid
water absorb energy and change to a gas
is called evaporation.
• In the water cycle, liquid water evaporates
from oceans, lakes, and other surfaces
and forms water vapor, a gas, in the
atmosphere.
• The energy for evaporation comes from
the heat of the sun.
The Water Cycle
Condensation
Precipitation
Evaporation
Evaporation from plants
Evaporation from lakes
Evaporation from oceans
Surface runoff
Groundwater
Condensation
• As the water vapor rises higher in the
atmosphere, it cools down. The cooled
vapor then turns back into tiny drops of
liquid water.
• The process by which a gas changes to a
liquid is called condensation.
Precipitation
• As more water vapor condenses, the drops of
water in the cloud grow larger.
• Eventually the heavy drops fall back to Earth as
precipitation—rain, snow, sleet, or hail.
• Most precipitation falls back into oceans or
lakes. The precipitation that falls on land may
soak into the soil and become groundwater.
The Carbon and Oxygen Cycles
• Two other substances necessary for life
are carbon and oxygen.
• Carbon is an essential building block in the
bodies of living things.
• Most organisms use oxygen for their life
processes.
Ecosystems
• In ecosystems, the processes by which
carbon and oxygen are recycled are
linked.
• Producers, consumers, and
decomposers play roles in recycling
carbon and oxygen.
Rising Carbon Dioxide Levels
When forests burn, large amounts
of carbon dioxide are released into
the air. In addition, there are
fewer trees available to absorb
carbon dioxide from the air.
Carbon and Oxygen Cycles
Carbon dioxide
in the atmosphere
Humans clear forests
for crops, releasing
carbon compounds
to the air
Humans burn fuels for
energy, releasing carbon
compounds to the air.
Plants take in
carbon dioxide
Animals break down
and use carbon
sugar molecules and
to make sugar
release carbon dioxide.
molecules.
Decomposers return
carbon compounds
to the soil and release
carbon dioxide to the air.
Animals take
in oxygen
Plants produce
oxygen.
The Nitrogen Cycle
Free nitrogen in air
Consumers eat nitrogen
compounds in plants.
Bacteria in the
soil release some
free nitrogen back
into the air.
Decomposers break
down wastes and
remains of organisms Plants use simple nitrogen
into simple nitrogen compounds to make proteins
compounds.
and other complex compounds
Bacteria in root
nodules fix free
nitrogen into
simple compounds.
The Nitrogen Cycle
• In the nitrogen cycle, nitrogen moves
from the air to the soil, into living
things, and back into the air.
• The process of changing free nitrogen into
a usable form of nitrogen is called
nitrogen fixation.
Nodules
• Some of these bacteria
live in bumps called
nodules (NAHJ oolz) on
the roots of certain
plants.
• These plants, known as
legumes, include clover,
beans, peas, alfalfa, and
peanuts.
Bacteria and Legumes
• The relationship
between the
bacteria and the
legumes is an
example of
mutualism. Both
the bacteria and
the plant benefit
from this
relationship.
Growth in Nitrogen-Poor Soil
• Pitcher plants
can grow in
nitrogen-poor soil
because they
have another
way of obtaining
nitrogen. Insects
become trapped
in the plant’s
tube-shaped
leaves. The plant
then
digests the
insects and uses
their nitrogen
compounds for
its functions.
Essential Questions
• What process causes water from the
surface of the ocean to enter the
atmosphere as water vapor?
Essential Questions
• What role do producers play in the
carbon and oxygen cycles?
Essential Questions
• Where do some nitrogen-fixing bacteria
live?